Gently drop your gold item into the water. Real gold is a heavy metal and will not float, so if your gold item floats you know it is not real gold. Also, if you notice rust or tarnishing on the item after being in water, this is also a sign it is not real gold since gold doesn't rust or tarnish.
The first test is also the easiest test: try to burn your gold. If it's real gold, it will get brighter as you apply the flame but it won't actually catch fire and burn. If your gold piece starts to smoke or gets darker, you likely have imitation gold.
The Skin Test
Just hold your gold item in your hand for a couple of minutes. If it's fake gold, the sweat on your skin will create a chemical reaction with the metal. Your skin will discolor to a black or green color. This is because it will react with the other alloy metals.
Along with your ornament, you will need a black stone similar to the jeweller's stone. Rub your piece of jewellery on the stone and add nitric acid to the mark. The acid will dissolve any other metals other than pure gold. If the mark dissolves upon applying nitrohydrochloric acid, it confirms the gold is pure.
Vinegar is very destructive, so when you apply the vinegar to a fake piece of gold, the vinegar will cause the jewelry to tarnish. Gold is a non-reactive metal, so real pieces of gold will not react to vinegar.
If it's real gold it will not stick to the magnet. (Fun fact: Real gold is not magnetic.) Fake gold, on the other hand, will stick to the magnet. If that necklace leaps to the magnet, your significant other has some explaining to do.
Goldmeter - real gold detector on the App Store.
Fool's Gold can be one of three minerals. The most common mineral mistaken for gold is pyrite. Chalcopyrite may also appear gold-like, and weathered mica can mimic gold as well.
Pure gold is notated as 24K – this is the highest karat level for gold meaning it is 100% pure gold. 18K gold is 75% purity level, 14K is 58.3% purity level, and 10K is 41.7% purity level. As you can see, the higher the karat number, the more pure gold comprises the metal.
While brass is not bright yellow, it's more dull than gold. However, gold is much shinier causing its golden color. Impurities can cause the shiny metallic luster that is characteristic of gold to fade. The purity of the gold determines the shine of ornaments.
Gold is not a magnetic metal, so if they pull towards the magnet, the beads are fake. However, if they don't react to the magnet, it doesn't necessarily mean they are real, as non-magnetic metals are used in counterfeit pieces as well.
Make a small scratch on the gold and add a drop of bleach. If it changes color, your jewelry is not 100% pure 24K gold. Bleach can permanently damage gold jewelry. It can't tell you if your gold is fake, since most gold jewelry has other metals mixed in to give it strength.
You will also need a small file or sandpaper to scratch the surface of the gold to be tested. To perform the test, first, scratch a small area of the gold with the file or sandpaper. This will remove the top layer of gold, exposing the inner layer. Next, apply a small drop of nitric acid to the scratched area.
Never use toothpaste, baking soda, or a commercial metal cleaner on gold. If you use these abrasives, you may scratch the gold. Never use bleach. Bleach reacts with gold and will eat away at gold alloys.
Gold is a relatively soft metal, and consequently gold coins that are made of pure gold or a high percentage of gold, can be relatively soft and malleable. Therefore, biting the coin would leave a mark or an indent if it was real gold.
Since gold is both paramagnetic and diamagnetic, both cancel one another out and become weak. So a strong magnet will attract gold ever so slightly and will also repel it.
Hold the magnet to your items
Gold is not magnetic so if the magnet attracts the jewelry, your item does not contain solid gold, silver or platinum.
Test With Nitric Acid
Make a mark deep enough to scratch through the top layer of gold. Carefully apply a drop of nitric acid to the mark, and determine if the mark turns green or milky. There will be no reaction if the jewelry is either gold or mostly gold.